The invention relates to a telecommunication system comprising at least a first and a second base station for wireless communication with a mobile terminal which before initiation of a handover procedure is wirelessly connected to the first base station and which after termination of the handover procedure is wirelessly connected to the second base station, which first base station is capable of being coupled to a data-packets switch by way of a first link and which second base station is capable of being coupled to the data-packets switch by way of a second link, with first data packets arriving by way of a first link comprising a first header part and a first data part, and second data packets arriving by way of the second link comprising a second header part and a second data part, and third data packets to be transmitted by way of a third link comprising a third header part and a third data part.
Such a telecommunication system is generally known. When, as a result of a displacement during communication, the mobile terminal comes into an overlapping part of the first coverage area of the first base station and the second coverage area of the second base station, the handover procedure is started. Before initiation of the handover procedure, there flow first data packets, by way of the first link, from the first base station to the data-packets switch which, in response thereto, transmits third data packets by way of the third link. After termination of the handover procedure, there flow second data packets, by way of the second link, from the second base station to the data-packets switch which, in response thereto, transmits third data packets by way of the third link. Since in each base station there is a buffer which buffers data packets, data packets could be lost during the handover procedure, particularly around the time of deactivation of the first wireless connection between the mobile terminal and the first base station, and of activation of the second wireless connection between the mobile terminal and the second base station. In order to prevent data packets getting lost, two possible solutions have been invented.
According to a first solution, there is applied an analyzing/converting device (a so-called UMTS Mobility Server or UMS) [UMTS=Universal Mobile Telecommunications System] in parallel to the data-packets switch. During the handover procedure, the analyzing/converting device by way of the data-packets switch receives all data packets from both base stations, analyzes the information present in these data packets, and combines and converts the data packets, whereafter a flow of third data packets obtained in this manner is transmitted by way of the data-packets switch. Apart from the need of placing an additional analyzing/converting device and the time consumed by analyzing, combining and converting, the analyzing/converting device has the drawback either that during the handover procedure three additional connections of the data-packets switch should be put into operation, which drastically reduces the effectiveness of the data-packets switch, or that the analyzing/converting device, not only during the handover procedure but during the complete communication, should be applied to a location situated between the base stations and the data-packets switch.
According to a second solution, the data-packets switch should break the coupling between the first link and the third link at the point in time on which the first buffer in the first base station is completely empty, and the data-packets switch should realize the coupling between the second link and the third link at exactly the same point in time, while up to this point in time the second buffer in the second base station is only allowed to buffer and not to let through, and exactly from this point in time onwards should generate stored data packets for transmission by way of the second link. The second solution (the so-called synchronized switching) has the drawback that in different locations simultaneous actions should be carried out with very great accuracy, which entails a great susceptibility to interference.